TeXmacs

Remarks: Although the name suggests it, neither TeX nor Emacs is required to get it compiled and running. TeXmacs is self-contained but needs guile-gtk for the interface. TeXmacs is in the overworks, and much of the internas (switching to cairo, etc.) and interface will change in the near future.

TiddlyWiki

Description: a single html file which has all the characteristics of a wiki